DOCSLIB.ORG

European Southern Observatory

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
European Southern Observatory EUROPEANSOUTHERNOBSERVATORY Organisation Europ´eennepour des Recherches Astronomiques dans l'H´emisph`ereAustral Europ¨aische Organisation f¨urastronomische Forschung in der s¨udlichen Hemisph¨are OBSERVING PROGRAMMES OFFICE • Karl-Schwarzschild-Straße 2 • D-85748 Garching bei M¨unchen • e-mail: [email protected] • Tel. : +49-89-32 00 64 73 APPLICATION FOR OBSERVING TIME PERIOD: 87A Important Notice: By submitting this proposal, the PI takes full responsibility for the content of the proposal, in particular with regard to the names of CoIs and the agreement to act according to the ESO policy and regulations, should observing time be granted 1. Title Category: A{6 Spectra of Galaxies Gravitationally Lensed by Abell 2744, the Largest Separation \Bullet Cluster" 2. Abstract / Total Time Requested Total Amount of Time: 0 nights VM, 9 hours SM Violent cluster mergers, when observed in the plane of our sky, place constraints on the physical nature of dark matter particles. These events are rare, and Abell 2744 is one of the best examples. This cluster merger is similar to the \Bullet Cluster" but more massive and with an even larger (the largest observed) separation between dark matter and the stripped, shocked cluster gas. Chandra X-ray observations of A2744 reveal extremely high temperature (> 15 keV) shock regions. We have obtained new deep multiband HST/ACS images of A2744's core to derive detailed dark matter maps. Our analyses reveal 30+ arcs produced by strong gravitational lensing. Spectroscopic redshifts of these arcs are essential to determine the masses of the merging clumps and constrain DM collsionality. None have been published to date. Therefore we are requesting 9 hours on VIMOS, primarily to obtain spectroscopic redshifts of strongly lensed arcs produced by this cluster. 3. Run Period Instrument Time Month Moon Seeing Sky Mode Type A 87 VIMOS 9h sep n 1.0 CLR s 4. Number of nights/hours Telescope(s) Amount of time a) already awarded to this project: b) still required to complete this project: 5. Special remarks: 6. Principal Investigator: Dan Coe, [email protected], US, Jet Propulsion Laboratory 6a. Co-investigators: B. Frye Other,US F. Braglia University of British Columbia,Department of Physics and Astronomy,CA R. Dupke Observatorio Nacional, MCT, CNPq,BR R. Massey Institute for Astronomy, The University of Edinburgh, Royal Observatory, Edinburgh,UK Following CoIs moved to the end of the document ... 7. Is this proposal linked to a PhD thesis preparation? State role of PhD student in this project - 1 - 8. Description of the proposed programme A { Scientific Rationale: The \Bullet Cluster" (1E0657-56) provides \direct empirical evidence for the existence of dark matter" (Markevitch04, Clowe04, Clowe06) and upper limits on the DM particle's self- 2 collisional cross section: σ=m ∼< 1cm =g (Randall08). This cluster merger appears to have followed this \simple" scenario: dark matter and galaxies passed directly through the collision while the hot cluster gas was shocked, stripped back, and left behind. This clearly reveals the different self-collisionalities of the various components, invalidating the simplest MOND/MOG hypotheses that DM is nothing but \missing mass" or \stronger gravity". As strong as this evidence is, the Bullet Cluster is but a single system. Additional cluster mergers must be studied, but these events are rare, and only a handful have been studied to date. The \Baby Bullet" (MACS J0025.4-1222; Bradac08) does appears to follow the Bullet Cluster scenario. However, analyses of two z ∼ 0:8 clusters (CL0152-14 and MS1054-03) seem to reveal galaxies slightly trailing the dark matter (with gas behind further still; Jee05a,b). And the initial analysis of Abell 520 (the \Cosmic Train Wreck"; Mahdavi07) suggested an opposite scenario, in which dark matter is stripped but gas is not! More recently, Abell 2146 was shown to have an X-ray structure very similar to the Bullet Cluster including a prominent bow shock, yet strangely the BCG trails the X-ray gas plume (Russel10). It seems that cluster mergers do not all follow a simple scenario, and additional analyses are warranted. The Abell 2744 cluster merger (z = 0:308) exhibits the largest observed separation between dark matter and X-ray gas (5400 ∼ 240 kpc, Shan10). Gas does appear to be stripped and left behind, though it has a complex temperature distribution along with a secondary gas clump residing to the NW. This NW gas clump may be unrelated, though recent work (Boehringer06, Braglia07,09) strongly suggests it is trailing a still infalling NW subcluster which is about to join the merger of two other clumps already in progress. Meanwhile, weak lensing analysis of VLT/FORS1 images (updated from the analyses presented in Cypriano04) show that the SE galaxies are slightly trailing the SE DM mass clump (Fig. 1). Again we find deviations from the simple scenario of gas being stripped from DM and galaxies. To map the DM structure of A2744 in more detail, we have obtained deep multiband Hubble Space Telescope imaging. Strong lensing analysis of these images reveals 30+ multiple images of 10+ background galaxies (Fig. 2). Similar to the Bullet Cluster analyses (Bradac06), we will obtain a robust mass model through simultaneous modeling of the strong + weak lensing observed in the HST and wider fields (here, VLT/FORS1). Our SL+WL analysis method (SaWLens; Merten09) has been demonstrated to yield reliable reconstructions of complicated mass distributions including cluster mergers similar to A2744. This method was applied to VLT/FORS and VLT/ISAAC data of MS2137-24. Spectroscopic redshifts for one or more the lensed arcs are essential to normalize our mass model, specifically, the mass of each merging subcluster. Arc redshift uncertainties can translate into uncertainties of a factor of ∼ 2 in the mass of each subclump (Bradac06). Currently no spectroscopic redshifts have been published for arcs lensed by A2744 (although see x10a and Fig. 4 right). Our ACS+VLT strong+weak lensing analyses including spectroscopic redshifts will provide robust and detailed maps of the DM in A2744's core. By comparing the positions of the DM clumps, galaxies, and X-ray gas clumps, we will help trace the merger history of this cluster. Furthermore, A2744 has a higher mass than the Bullet Cluster, offering the potential for tighter constraints on the dark matter self-interaction cross section. Ancillary science (spectra to be obtained in parallel): We will increase the completeness of spectral coverage in the central regions of the cluster (Fig. 4 left), including fainter cluster members (I ∼> 22). This will provide us with more precise estimates of: 1) the dynamical mass (Biviano06; to be compared with the lensing and X-ray derived masses and used in joint analyses); 2) kinematics in the high line-of-sight velocity core, revealing how the velocity distribution is affected by the ongoing merger; 3) galaxy blue fraction as a function of magnitude / stellar mass (Couch98). We will also target some especially blue cluster members to investigate possible star-formation activity enhance- ments in cluster galaxies due to harassment (e.g., the “flaming giants" detected by Braglia et al. 2007) and/or ram pressure stripping. One especially enigmatic galaxy worthy of further study is highlighted in Fig. 3. B { Immediate Objective: We will obtain multislit spectroscopy at R = 600 to measure redshifts for a sufficiently bright subset of our ∼ 30 images of ∼ 10 galaxies strongly lensed by Abell 2744. We will also study the spectral features of the IGM along the lines of sight to the arcs (Frye07,08). In parallel, we will obtain spectra of cluster galaxies as described above. We will include blue cluster galaxies, planning to measure the star formation rates, ISM gas turbulence and physical conditions based on the line fluxes, line widths, and line profiles of the available emission lines. Regarding our Fig. 3 galaxy, NTT/EMMI data reveal [OIII]λ5007 and Hβ (Boschin06: ID90). We will also search for additional Balmer series lines to deduce the reddening as well as [OII], [OIII], [SiII] and [NII] to better understand the physical and evolutionary state of this dynamically-disturbed spiral galaxy. - 2 - 8. Description of the proposed programme and attachments Fig. 1: Abell 2744 exhibits the largest observed separation Fig. 2: Based on strong lens modeling of (~54′′ ~240 kpc; Shan10) between dark matter (shown here in our HST/ACS images, we have identified blue) and hot cluster gas (red, from Chandra) overlaid on our 30+ multiple images of 10+ background newly-obtained HST/ACS images (BVi color image, 3.5′ × 2.8′ objects. Spectroscopic redshifts of these section). The dark matter map is an updated version of that arcs are essential to determine mass of this obtained via weak lensing analysis in Cypriano04. The (SW) clump as well as normalize the full galaxies at left appear to be slightly trailing the dark matter. mass model. The other clumps exhibit This would be interesting, as hints of this have been seen fewer arcs, but their spec-z will be equally elsewhere (Jee05a,b). We are improving this DM map important. Spec-z have yet to be obtained significantly by including strong and weak lensing constraints for any A2744 arcs (although see Fig. 4). which we have obtained from HST/ACS data (Fig. 2). The HST/ACS BVi image stamp: 100′′×100′′ bright X-ray source is featured in Fig. 3. (1′′ ~ 4.3 kpc). Fig. 3: This galaxy appears to be undergoing prominent ram pressure stripping and star formation as it plows through Fig. 4: Left – Many A2744 cluster galaxies remain without confident the cluster gas. It is also a very spectroscopic redshifts. Overlaid on the VLT/FORS1 VRI and HST/ACS bright X-ray source, likely BVi color images are objects with published redshifts in the central ~7′×7′ indicating a central AGN (or from Braglia09 VLT/VIMOS (spec-z, squares) and Boschin06 perhaps intense star formation).
Load more

Recommended publications
  • Arxiv:1903.02002V1 [Astro-Ph.GA] 5 Mar 2019
    Draft version March 7, 2019 Typeset using LATEX twocolumn style in AASTeX62 RELICS: Reionization Lensing Cluster Survey Dan Coe,1 Brett Salmon,1 Maruˇsa Bradacˇ,2 Larry D. Bradley,1 Keren Sharon,3 Adi Zitrin,4 Ana Acebron,4 Catherine Cerny,5 Nathalia´ Cibirka,4 Victoria Strait,2 Rachel Paterno-Mahler,3 Guillaume Mahler,3 Roberto J. Avila,1 Sara Ogaz,1 Kuang-Han Huang,2 Debora Pelliccia,2, 6 Daniel P. Stark,7 Ramesh Mainali,7 Pascal A. Oesch,8 Michele Trenti,9, 10 Daniela Carrasco,9 William A. Dawson,11 Steven A. Rodney,12 Louis-Gregory Strolger,1 Adam G. Riess,1 Christine Jones,13 Brenda L. Frye,7 Nicole G. Czakon,14 Keiichi Umetsu,14 Benedetta Vulcani,15 Or Graur,13, 16, 17 Saurabh W. Jha,18 Melissa L. Graham,19 Alberto Molino,20, 21 Mario Nonino,22 Jens Hjorth,23 Jonatan Selsing,24, 25 Lise Christensen,23 Shotaro Kikuchihara,26, 27 Masami Ouchi,26, 28 Masamune Oguri,29, 30, 28 Brian Welch,31 Brian C. Lemaux,2 Felipe Andrade-Santos,13 Austin T. Hoag,2 Traci L. Johnson,32 Avery Peterson,32 Matthew Past,32 Carter Fox,3 Irene Agulli,4 Rachael Livermore,9, 10 Russell E. Ryan,1 Daniel Lam,33 Irene Sendra-Server,34 Sune Toft,24, 25 Lorenzo Lovisari,13 and Yuanyuan Su13 1Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA 2Department of Physics, University of California, Davis, CA 95616, USA 3Department of Astronomy, University of Michigan, 1085 South University Ave, Ann Arbor, MI 48109, USA 4Physics Department, Ben-Gurion University of the Negev, P.O.
    [Show full text]
  • Radio Observations of the Merging Galaxy Cluster Abell 520 D
    A&A 622, A20 (2019) Astronomy https://doi.org/10.1051/0004-6361/201833900 & c ESO 2019 Astrophysics LOFAR Surveys: a new window on the Universe Special issue Radio observations of the merging galaxy cluster Abell 520 D. N. Hoang1, T. W. Shimwell2,1, R. J. van Weeren1, G. Brunetti3, H. J. A. Röttgering1, F. Andrade-Santos4, A. Botteon3,5, M. Brüggen6, R. Cassano3, A. Drabent7, F. de Gasperin6, M. Hoeft7, H. T. Intema1, D. A. Rafferty6, A. Shweta8, and A. Stroe9 1 Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, The Netherlands e-mail: [email protected] 2 Netherlands Institute for Radio Astronomy (ASTRON), PO Box 2, 7990 AA Dwingeloo, The Netherlands 3 INAF-Istituto di Radioastronomia, via P. Gobetti 101, 40129 Bologna, Italy 4 Harvard-Smithsonian for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 5 Dipartimento di Fisica e Astronomia, Università di Bologna, via P. Gobetti 93/2, 40129 Bologna, Italy 6 Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany 7 Thüringer Landessternwarte, Sternwarte 5, 07778 Tautenburg, Germany 8 Indian Institute of Science Education and Research (IISER), Pune, India 9 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany Received 18 July 2018 / Accepted 10 September 2018 ABSTRACT Context. Extended synchrotron radio sources are often observed in merging galaxy clusters. Studies of the extended emission help us to understand the mechanisms in which the radio emitting particles gain their relativistic energies. Aims. We examine the possible acceleration mechanisms of the relativistic particles that are responsible for the extended radio emis- sion in the merging galaxy cluster Abell 520.
    [Show full text]
  • BEC Dark Matter Can Explain Collisions of Galaxy Clusters
    BEC dark matter can explain collisions of galaxy clusters Jae-Weon Lee∗ School of Computational Sciences, Korea Institute for Advanced Study, 207-43 Cheongnyangni 2-dong, Dongdaemun-gu, Seoul 130-012, Korea Sooil Lim Department of Physics and Astronomy, Seoul National University, Seoul, 151-747, Korea Dale Choi∗ Korea Institute of Science and Technology Information, Kwahanro 335, Yuseong-Gu, Daejeon, 305-806, South Korea (Dated: October 31, 2018) We suggest that the dark matter model based on Bose Einstein condensate or scalar field can resolve the apparently contradictory behaviors of dark matter in the Abell 520 and the Bullet cluster. During a collision of two galaxies in the cluster, if initial kinetic energy of the galaxies is large enough, two dark matter halos pass each other in a soliton-like way as observed in the Bullet cluster. If not, the halos merge due to the tiny repulsive interaction among dark matter particles as observed in the Abell 520. This idea can also explain the origin of the dark galaxy and the galaxy without dark matter. PACS numbers: 98.62.Gq, 95.35.+d, 98.8O.Cq Dark matter (DM) constituting about 24 percent of and lag behind the other matters at the collision center. the mass of the universe is one of the big puzzles in mod- The distribution of DM can be inferred by optical tele- ern physics and cosmology [1, 2] . According to numeri- scopes using the gravitational lensing effect, while that of cal simulations, while the cold dark matter (CDM) with the hot gases by X-ray telescopes like Chandra.
    [Show full text]
  • Axion-Higgs 3-Dimensional Rigid Transformable Strings and the Compound 650 Gev Z-Z Decay Into Quarks/Leptoquarks
    The Magic of Life- and Matter Creating Self Propelled Electric Dark Matter Black Holes Guided by a Holographic Entangled Symmetric Multiverse System. Leo Vuyk, Architect, Rotterdam, the Netherlands. Abstract, In Quantum Function Follows Form Theory, ( Q-FFF Theory) the Big Bang was the evaporation and splitting of a former Big Crunch black hole nucleus of compressed massless Axion Higgs particles. The Big Bang Nucleus of compressed massless Axion /Higgs particles is assumed to be split into respectively chunky nuclei of dark matter black holes called plasma /matter creating Quasars, or evaporated as singular massless Axion Higgs vacuum particles oscillating along a tetrahedral shaped chiral vacuum lattice. The vacuum Lattice is supposed to represent a dynamic reference frame with variable local length and so called Dark Energy or Zero Point Energy acting as the motor for all Fermion spin and eigen energy and as the transfer medium for all photon information, leading to local lightspeed and local time. The energetic oscillating vacuum lattice is assumed to act as a Gravity Quantum Dipole Repeller (or large scale Casimir effect) Gravitons are not supposed to attract- but repel Fermions with less impulse than vacuum particle pressure does. So, gravity is assumed to be a dual pressure process on fermions. As a consequence, Feynman diagrams become more complex than before.. Recent measurements by Yehuda Hoffman et al. did show the repelling effect of “empty space” in opposition of the “attracting gravity effect” of super clusters which he called “Dipole Repeller” effect. The universe is supposed to be Holographic by the instant long distance entanglement particle guidance between Charge Parity Symmetric Universes; the Multiverse.
    [Show full text]
  • Cycle 16 Approved Programs
    Cycle 16 Approved Programs First Name Last Name Type Phase II ID Institution Country Science Category Title Brigham Young Searching For Unresolved Binary Brown Jacob Albretsen AR 11238 USA Cool Stars University Dwarfs Using Point Spread Functions Fermi National A Unique High Resolution Window to Two Sahar Allam GO 11167 Accelerator USA Cosmology Strongly Lensed Lyman Break Galaxies Laboratory (FNAL) New Sightlines for the Study of Intergalactic University of Quasar Absorption Scott Anderson GO 11215 USA Helium: Dozens of High-Confidence, UV- Washington Lines and IGM Bright Quasars from SDSS/GALEX Rutgers the State Unresolved Stellar NICMOS imaging of submillimeter galaxies Andrew Baker GO 11143 University of New USA Populations with CO and PAH redshifts Jersey University of ISM and Bruce Balick GO 11122 USA Expanding PNe: Distances and Hydro Models Washington Circumstellar Matter Identifying Atomic and Molecular Absorption Travis Barman AR 11239 Lowell Observatory USA Cool Stars in an Extrasolar Planet Atmosphere University of Texas at George Benedict GO 11210 USA Cool Stars The Architecture of Exoplanetary Systems Austin University of Texas at Resolved Stellar An Astrometric Calibration of Population II George Benedict GO 11211 USA Austin Populations Distance Indicators Space Telescope Monitoring the Giant Flare of HST-1 in the John Biretta GO 11216 USA AGN/Quasars Science Institute M87 Jet Roger Blandford AR 11288 Stanford University USA Cosmology PASS: Paying Attention to the Small Structure Space Telescope ISM and Howard Bond GO 11217
    [Show full text]
  • University of Virginia Department of Astronomy Leander Mccormick Observatory Charlottesville, Virginia, 22903-0818 ͓S0002-7537͑95͒02201-3͔
    1 University of Virginia Department of Astronomy Leander McCormick Observatory Charlottesville, Virginia, 22903-0818 ͓S0002-7537͑95͒02201-3͔ This report covers the period 1 September 2003 to 31 Theory, Long Term Space Astrophysics, Origins of Solar August 2004. Systems, and XMM programs, JPL, Chandra, Space Tele- scope Science Institute, and the NSF Stars/Stellar Systems 1. PERSONNEL and Gravitational Physics Programs. During this time the departmental teaching faculty con- sisted of Steven A. Balbus, Roger A. Chevalier, John F. 2. FACILITIES Hawley, Zhi-Yun Li, Steven R. Majewski, Edward M. The Leander McCormick Observatory with its 26-in Murphy, Robert W. O’Connell, Robert T. Rood, Craig L. Clark refractor on Mount Jefferson is now used exclusively Sarazin, William C. Saslaw, Michael F. Skrutskie, Trinh X. for education and public outreach. It is heavily used for both Thuan, Charles R. Tolbert, and D. Mark Whittle. our graduate and undergraduate courses. The Public Night Research scientists associated with the department were program has been expanded. During the year a plan to Gregory J. Black, Richard J. Patterson, P. Kenneth Seidel- greatly expand the education and public outreach program mann, Anne J. Verbiscer, John C. Wilson, and Kiriaki M. was initiated. This is described in § 4. Xilouris. The 0.7-m and the 1-m reflectors on Fan Mountain were Robert E. Johnson from Materials Science has his re- used during the year for our undergraduate majors and search group in planetary astronomy located within the de- graduate observational astronomy courses. A major upgrade partment. In retirement both Laurence W. Fredrick and of instrumentation is underway and is described in § 3.7.
    [Show full text]
  • Probing Quantum Gravity Through Strong Gravitational Lensing
    Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 14 February 2018 doi:10.20944/preprints201712.0093.v2 Probing Quantum Gravity through Strong Gravitational Lensing S Marongwe1, Department of Physics and Astronomy Botswana International University of Science and Technology, P. Bag 16, Palapye, Botswana E-mail: [email protected] Abstract. We report the use of Einstein rings to reveal the quantized and dynamical states of space-time in a region of impressed gravitational field as predicted by the Nexus Paradigm of quantum gravity. This in turn reveals the orbital speeds of objects found therein and the radius of curvature of the quantized space-time. Similarities between the Nexus graviton and the singular isothermal sphere (SIS) in the Cold Dark Matter (CDM) paradigm are highlighted. However unlike the singular isothermal sphere, the Nexus graviton does not contain singularities or divergent integrals. This solves the core cusp problem. In this work, data from a sample of fifteen Einstein rings published on the Cfa-Arizona Space Telescope Lens Survey (CASTLES) website is used to probe the quantized properties of space-time. Keywords: (Quantum Gravity; Gravitational Lensing; Dark Matter; Quantum Vacuum; Graviton) Introduction In 1937, Zwicky (Zwicky 1937 ) provided the first reproducible evidence of the presence of unseen matter in the Coma Cluster group of galaxies by applying the classic virial theorem where he also suggested that the gravitational field of galaxy clusters is expected to deflect the light observed from background galaxies. Today, numerous observations (Boller 1989, 1 To whom any correspondence should be addressed. 1 © 2018 by the author(s). Distributed under a Creative Commons CC BY license.
    [Show full text]
  • Arxiv:1405.0222V2 [Astro-Ph.CO] 22 Oct 2014
    Accepted to ApJ: draft date October 23, 2014 Preprint typeset using LATEX style emulateapj v. 5/2/11 LENS MODELS AND MAGNIFICATION MAPS OF THE SIX HUBBLE FRONTIER FIELDS CLUSTERS∗ Traci L. Johnson1, Keren Sharon1, Matthew B. Bayliss2,3, Michael D. Gladders4,5, Dan Coe6, Harald Ebeling7 Accepted to ApJ: draft date October 23, 2014 ABSTRACT We present strong-lensing models, as well as mass and magnification maps, for the cores of the six HST Frontier Fields galaxy clusters. Our parametric lens models are constrained by the locations and redshifts of multiple image systems of lensed background galaxies. We use a combination of photometric redshifts and spectroscopic redshifts of the lensed background sources obtained by us (for Abell 2744 and Abell S1063), collected from the literature, or kindly provided by the lensing community. Using our results, we (1) compare the derived mass distribution of each cluster to its light distribution, (2) quantify the cumulative magnification power of the HFF clusters, (3) describe how our models can be used to estimate the magnification and image multiplicity of lensed background sources at all redshifts and at any position within the cluster cores, and (4) discuss systematic effects and caveats resulting from our modeling methods. We specifically investigate the effect of the use of spectroscopic and photometric redshift constraints on the uncertainties of the resulting models. We find that the photometric redshift estimates of lensed galaxies are generally in excellent agreement with spectroscopic redshifts, where available. However, the flexibility associated with relaxed redshift priors may cause the complexity of large-scale structure that is needed to account for the lensing signal to be underestimated.
    [Show full text]
  • The Dynamics of Merging Clusters: a Monte Carlo Solution Applied to the Bullet and Musket Ball Clusters
    Introduction The method Applications Summary The Dynamics of Merging Clusters: A Monte Carlo Solution Applied to the Bullet and Musket Ball Clusters William A. Dawson University of California, Davis, Physics Department 5 de setembro de 2013 Seminário do grupo de Extragaláctica Departamento de Astronomia - IAG/USP William A. Dawson The Dynamics of Merging Clusters: A Monte Carlo Solution Applied to the Bullet Introduction The method Applications Summary Outline 1 Introduction Why the study of merging cluster are important? Dissociative mergers Merging configuration Problems Methods to study the merger dynamics A new method 2 The method Model Monte Carlo Analysis 3 Applications Bullet Cluster dynamics Musket Ball dynamics 4 Summary William A. Dawson The Dynamics of Merging Clusters: A Monte Carlo Solution Applied to the Bullet Why the study of merging cluster are important? Introduction Dissociative mergers The method Merging configuration Applications Problems Summary Methods to study the merger dynamics A new method Why the study of merging cluster are important? Merging clusters are important probes to σDM (e.g. Bullet Cluster) and the large-scale matter-antimatter ratio (e.g. Steigman 08); The best constraints come from M/L of the sub-clusters and the offset between the collisionless galaxies and DM; both depends on the merger dynamics (basically the velocity of collision (1) and the time since collision (2)); (1) will affect the the expected momentum transfer between each sub-clusterâs dark matter particles → affect the expected dark matter mass transfer from the smaller to the largest sub-cluster → affect the expected M/L; (2) the galaxy-DM offset depends on the time-since-collision (TSC); initially the offset will increase with TSC (for σDM > 0) as the galaxies outrun the DM → at later TSC the offset will decrease due to the gravitational attraction (galaxies + DM).
    [Show full text]
  • Mirror Dark Matter Discovered?
    Mirror dark matter discovered? Z.K. Silagadze Budker Institute of Nuclear Physics and Novosibirsk State University 630 090, Novosibirsk, Russia Recent astrophysical data indicates that dark matter shows a contro- versial behaviour in galaxy cluster collisions. In case of the notorious Bullet cluster, dark matter component of the cluster behaves like a collisionless system. However, its behaviour in the Abell 520 cluster indicates a sig- nificant self-interaction cross-section. It is hard for the WIMP based dark matter models to reconcile such a diverse behaviour. Mirror dark matter models, on the contrary, are more flexible and for them diverse behaviour of the dark matter is a natural expectation. PACS numbers: 95.30.-k, 95.35.+d, 11.30.Er 1. Introduction The evidence of dark matter is compelling at all observed astrophysical scales [1, 2]. At that the dark matter reveals itself only through its grav- arXiv:0808.2595v2 [astro-ph] 20 Aug 2008 itational interactions. There are no observational facts that indicate exis- tence of any significant interactions between the ordinary and dark matter particles. However, some recent astrophysical observations show that dark matter particles may have significant self-interactions. This is surprising be- cause other observations support the WIMP paradigm that the dark matter is essentially collisionless. The mirror dark matter [3, 4, 5], first introduced in [6], has a potential to reconcile these seemingly contradictory observa- tional facts. For other attempts to do this, on the base of BEC dark matter, see [7]. Below, after briefly commenting the mirror matter idea, we consider the above mentioned observational facts and argue why, in our opinion, they indicate the existence of the mirror matter as the main dark matter component.
    [Show full text]
  • Feedback in Galaxy Clusters and Brightest Cluster Galaxy Star
    Feedback in Galaxy Clusters and Brightest Cluster Galaxy Star Formation by Kevin Fogarty A dissertation submitted to The Johns Hopkins University in conformity with the requirements for the degree of Doctor of Philosophy. Baltimore, Maryland August, 2017 c Kevin Fogarty 2017 All rights reserved Abstract My main thesis work is to understand the relationship between star forma- tion in the brightest cluster galaxy (BCG) and the thermodynamical state of the intracluster medium (ICM) of cool core galaxy clusters. Detailed photometry of BCGs in galaxy clusters observed in the Cluster Lensing and Supernova survey with Hubble (CLASH) reveal ultraviolet and Hα emitting knot and filamentary structures extending several tens of kpc. I initially focus on these structures, −1 which harbor starbursts forming stars at rates between < 1 M yr and ∼ −1 250 M yr . I perform ultraviolet through far-infrared Spectral Energy Dis- tribution (SED) fitting on combined Hubble, Spitzer, and Herschel photometry of CLASH BCGs, and measure star formation rates (SFRs), dust contents, and constrain the duration of starburst activity. Using X-ray data from Chandra, I find a tight relationship between CLASH BCG SFRs and the cooling-to-freefall time ratio in the ICM. I propose treating the cooling-to-freefall time ratio as a proxy for the mass condensation efficiency of the ICM in the core of cool-core clusters, an interpretation which is motivated by recent theoretical work de- ii ABSTRACT scribing feedback regulated condensation and precipitation of the ICM in cool core clusters. I follow up this work by performing similar SED fitting on a larger sample of clusters observed in the Cosmic Evolution Survey (COSMOS).
    [Show full text]
  • Colliding Clusters and Dark Matter Self-Interactions
    Mon. Not. R. Astron. Soc. 000, 000{000 (0000) Printed 20 January 2014 (MN LATEX style file v2.2) Colliding clusters and dark matter self-interactions Felix Kahlhoefer,1? Kai Schmidt-Hoberg,2 Mads T. Frandsen3 and Subir Sarkar1;4 1 Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, United Kingdom 2 Theory Division, CERN, 1211 Geneva 23, Switzerland 3 CP3-Origins and the Danish Institute for Advanced Study, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark 4 Niels Bohr Institute, Blegdamsvej 17, 2100 København Ø, Denmark 20 January 2014 ABSTRACT When a dark matter halo moves through a background of dark matter particles, self- interactions can lead to both deceleration and evaporation of the halo and thus shift its centroid relative to the collisionless stars and galaxies. We study the magnitude and time evolution of this shift for two classes of dark matter self-interactions, viz. frequent self-interactions with small momentum transfer (e.g. due to long-range interactions) and rare self-interactions with large momentum transfer (e.g. contact interactions), and find important differences between the two cases. We find that neither effect can be strong enough to completely separate the dark matter halo from the galaxies, if we impose conservative bounds on the self-interaction cross-section. The majority of both populations remain bound to the same gravitational potential and the peaks of their distributions are therefore always coincident. Consequently any apparent separation is mainly due to particles which are leaving the gravitational potential, so will be largest shortly after the collision but not observable in evolved systems.
    [Show full text]